Reading raw data | Qnbot Docs Center

This chapter covers values produced directly by the device firmware, with no algorithm package: after start(), pose is published with valid device frames, and IMU is published when a device frame carries it. run_forever(), run_background() and update() neither generate this data nor change its publishing rate. For the full source description, see Data channels & read methods.

Glove pose

device.pose() should be obtained after the SDK is created and the device is selected. When processing pose continuously, put the parsing logic into a callback and register it before startup:

from threading import Event

from qnbot_sdk import Sdk
from qnbot_sdk.glove import GloveConfig

def on_pose(sample):
    pose = sample.value
    print(pose.meta.source)
    print(pose.payload.root_pose.position)
    print(pose.payload.root_pose.quaternion_xyzw)
    print(pose.payload.fingertip_world)
    print(pose.payload.fingertip_local)
    print(pose.payload.raw_valid_mask)
    print(pose.payload.held_mask)
    print(pose.payload.quality_flags)

sdk = Sdk(devices=(GloveConfig(),))
glove = sdk.glove()
try:
    glove.device().pose().subscribe(on_pose)
    glove.start()
    Event().wait()
finally:
    glove.close()

Choose a read path by what you need:

What you want to do	Read path
Split frames by their source (several gloves or inputs)	`meta.source`
Place the wrist or palm	`payload.root_pose`
Put a virtual hand in world coordinates, drive an external skeleton	`payload.fingertip_world`
Retarget or compute against the wrist	`payload.fingertip_local`
Skip fingers whose raw data is invalid	`payload.raw_valid_mask`
Spot fingers reusing their previous valid value	`payload.held_mask`
Judge the quality of the whole frame	`payload.quality_flags`

For complete fields, types and nullability behavior, see GlovePose and GloveFeaturePayload.

IMU (experimental feature)

device.imu() is used to read the GloveImu raw counts provided by a USB serial device in the data JSON:

from threading import Event

from qnbot_sdk import Sdk
from qnbot_sdk.glove import GloveConfig

def on_imu(sample):
    imu = sample.value
    print(imu.payload.valid)
    print(imu.payload.gyroscope_raw)
    print(imu.payload.accelerometer_raw)

sdk = Sdk(devices=(GloveConfig(),))
glove = sdk.glove()
try:
    glove.device().imu().subscribe(on_imu)
    glove.start()
    Event().wait()
finally:
    glove.close()

gyroscope_raw and accelerometer_raw are both three signed 16-bit integers, corresponding in order to the three axes in the device protocol. The SDK does not perform unit conversion, calibration or pose fusion on this data. When valid is False, the raw counts are still retained and published; you can decide whether to use them according to your actual use case. Currently only IMU in wired USB serial JSON is supported; the binary IMU of the wireless receiver is not supported in this version.

Choose a read path by what you need:

What you want to do	Read path
Tell whether this reading can be used	`payload.valid`
Read the raw three-axis gyroscope counts	`payload.gyroscope_raw`
Read the raw three-axis accelerometer counts	`payload.accelerometer_raw`

For complete fields, types and nullability behavior, see GloveImu and GloveImuPayload.

Device status

device.status() is also produced directly by the device rather than computed: whether it is connected, whether data is stale, the last error and the reconnect count. See Diagnostics & errors for the fields and how to use them for diagnosis.